This application relies for priority upon Korean Patent Application No. 2001-25409, filed on May 10, 2001, the contents of which are herein incorporated by reference in their entirety.
1. Field of the Invention
The present invention relates to the field of semiconductor manufacturing and, more particularly to a wafer sawing apparatus.
2. Description of the Related Art
As well known in the field, a semiconductor product is manufactured by a series of steps of semiconductor wafer fabrication, packaging, and test. Through the wafer fabrication, circuits or devices are formed on a surface of a semiconductor wafer. Then, the processed wafer is sawed (singulated) into individual semiconductor chips. Each of the individual chips subsequently is subsequently assembled in a package.
In the conventional wafer-sawing step, the wafer is mounted on a chuck table and sawed with a diamond-headed blade. A full-cutting method is used in order to easily separate the chips on the wafer into individual chips. In the full-cutting method case, an adhesive tape is attached to the back surface of the wafer and both are cut. Therefore, the scribing blade is set to have a predetermined cutting depth, so as to completely cut the wafer or to partially cut the adhesive tape by approximately 20%.
Since the adhesive tape is of a thickness of only roughly 30-70 microns and the wafer is of a thickness of only several hundred microns, it is difficult to precisely control the cutting depth. Even if the cutting depth of the scribing blade is controlled, numeric error of the cutting depth may easily occur. Moreover, data input errors of only several microns to several dozen microns can cause wafer cutting failures.
Further, inconsistent abrasion rates of the scribing blade also cause the wafer cutting failures.
If the cutting depth of the scribing blade is set to be more than the total thickness of the wafer and the adhesive tape, the scribing blade may damage the chuck table.
Since the wafer cutting failures affect multiple stacked wafers, they are fatally defective errors.
Accordingly, an object of the present invention is to prevent wafer cutting failures due to over-sawing of the wafer and to prevent the chuck table from being damaged by the scribing blade.
The foregoing and other objects are achieved by a wafer sawing apparatus comprising a chuck table including a wafer suction plate for mounting and retaining a wafer, an electrically conductive table body surrounding the wafer suction plate, and tactile sensing lines being formed on the upper surface of the wafer suction plate, at least one end of the tactile sensing line being electrically connected to the table body. A scribing blade for sawing the wafer is mounted on the chuck table; a controller, for controlling the chuck table and the scribing blade, is electrically connected to the table body of the chuck table and the scribing blade. The controller comprises a tactile sensing unit for sensing the contact of the scribing blade with the tactile sensing lines or the table body, the tactile sensing unit being connected to the table body; and an equipment stop unit for stopping the driving of the scribing blade by receiving a signal of the contact of the scribing blade with the tactile sensing lines from the tactile sensing unit.
The controller of the present invention further comprises a zero point adjusting unit for receiving the signal of the contact from the tactile sensing unit and for adjusting a zero point of the scribing blade; and a switching unit for opening or closing a connection between the tactile sensing unit and the zero point adjusting unit or a connection between the tactile sensing unit and the equipment stop unit. In adjusting the zero point, the switching unit connects the tactile sensing unit to the zero point adjusting unit, and then in sawing the wafer, the switching unit connects the tactile sensing unit to the equipment stop unit.
The tactile sensing lines comprises at least one first tactile sensing line intersecting with horizontal scribe lines along which the scribing blade saws the wafer; and at least one second tactile sensing line intersecting with vertical scribe lines along which the scribing blade saws the wafer.
In a first preferred aspect of the present invention, the first tactile sensing line is perpendicular to the horizontal scribe lines of the wafer and the second tactile sensing line is perpendicular to the vertical scribe lines of the wafer.
In a second preferred aspect of the present invention, a plurality of tactile sensing lines form a substantially bounding the sawing area.
In a third preferred aspect of the present invention, the tactile sensing lines comprises a first tactile sensing line in a circle substantially encircling the area formed by connecting two outermost vertical scribe lines and two outermost horizontal scribe lines of the wafer; and a second tactile sensing line for connecting the first tactile sensing line to the table body.
In accordance with the preferred embodiments of the present invention, since the tactile sensing lines on the chuck table senses a contact of the scribing blade with the wafer suction plate of the chuck table due to the over-sawing of the scribing blade on the wafer, the wafer sawing apparatus of the present invention prevents wafer cutting failures and prevents the chuck table from being damaged by a scribing blade.